1. Field of the Invention
The invention relates to compositions and methods for producing benzylisoquinoline alkaloids (BIAs) or molecules involved in the production of BIAs. The compositions comprise host cells comprising at least one heterologous coding sequence that encodes for an enzyme or its equivalent that is involved in the BIA synthetic pathway.
2. Background of the Invention
Alkaloids are a diverse group of nitrogen-containing small molecules that are produced in plants, marine organisms, and microorganisms through complex biosynthetic pathways. These complex molecules exhibit a range of interesting pharmacological activities and have been used as antimalarials, anticancer agents, analgesics, and in treatment of parkinsonism, hypertension, and central nervous system disorders.
The benzylisoquinoline alkaloids (BIAs) are a family of alkaloid molecules with over 2,500 defined structures. The most common BIAs currently utilized as medicinal compounds are synthesized in the opium poppy and include the analgesics codeine and morphine. However, many intermediates in this pathway that do not accumulate to significant levels in plants are themselves pharmacologically active as analgesics, antimalarials, anticancer agents, and antimicrobial agents. Even for molecules that accumulate to high levels in plants, it would be advantageous to eliminate the rigorous extraction and purification procedures required to isolate these compounds.
Chemical synthesis of these types of molecules is normally a costly and time-consuming process, often requiring harsh process conditions, generating toxic waste streams, and resulting in low quantities of the chemicals. In addition, many structures are simply unattainable using traditional synthesis methods due to the number of chiral centers and reactive functional groups. Alternatively, the production of BIAs can be achieved at relatively low cost and high yields in a microbial host. This will allow for cost-effective large scale production of intermediate and end-product BIAs.
The inventors have developed methods and compounds for the production of complex BIAs and their intermediates. Specifically, one can generate these molecules by expressing cloned and synthetic cDNAs in the host organism such that precursor molecules naturally produced in yeast, specifically L-tyrosine, are converted to various BIA intermediates in these engineered strains through a series of specific reactions catalyzed by recombinant enzymes. Engineered yeast strains can also be used to convert more complex substrates into value-added BIA molecules using similar strategies. The novel technology developed is the production of this family of alkaloid molecules in yeast from simple precursor molecules and/or more complex substrates using yeast or another microorganism as a host for the production of these molecules. Various BIA intermediates will be produced in yeast and can be used directly for their pharmacological activities or they can be used as starting molecules for chemical synthesis modifications to place additional functional groups on these backbone molecules to alter their pharmacological activities. For instance, one important intermediate reticuline is a molecule from which a number of pharmacologically active molecules such as sanguinarine and codeine can be synthesized. In addition, host cells can be engineered to produce non-natural alkaloid derivatives by adding novel enzymatic conversion steps to the heterologous pathway or eliminating steps from the native or heterologous pathway.
Microbial biosynthesis enables green synthesis and the production of these molecules without extreme reaction conditions and toxic waste streams. Furthermore, many intermediates of interest do not accumulate in the native plant hosts, and studies have demonstrated that modifying expression of specific genes in this pathway in the native plant hosts in order to direct accumulation of specific intermediates often inactivates multiple enzymes in the pathway, prohibiting the rational engineering of plant strains to accumulate specific intermediates. Microbial biosynthesis also eliminates the need for rigorous extraction and purification procedures required to isolate target molecules from the native host.